Bigger vessels calling to the Port of Long Beach and a shift in business from Los Angeles to Long Beach continue to impact the amount of cargo flowing through the twin ports.

Posting some of its biggest numbers in almost three years, cargo volumes for May at the Port of Long Beach maintained their double-digit rise, according to statistics released Monday.

Cargo at the Port of Long Beach jumped 17.2 percent in May from the same time a year ago for a total of 583,588 container units.

Imports spiked 22.2 percent to 305,498 units, the largest rise since August 2010, while exports rose 13.9 percent to 147,073 units, the most since October 2010, according to the port.

Empty containers, which are shipped overseas to be replenished with products, also rose 10.2 percent to 131,017 units.

Meanwhile, the Port of Los Angeles last week reported declining cargo numbers for May. Los Angeles posted a 12.9 percent drop to 636,851 units in May, compared to last year.

Imports also fell 12 percent to 326,114 units, and exports dropped 16.3 percent to 154,004 units last month compared to May 2012.

The shift in cargo numbers between the neighboring ports has been occurring since late 2012, when Mediterranean Shipping Co. moved its business from Los Angeles to Long Beach.

Long Beach has been working to boost its business, obtaining commitments from shipping lines OOCL, MSC and France-based ocean carrier CMA CGM to expand their footprints at the port.

CMA intends to lease and run a 256-acre terminal at Pier J for a West Coast hub, which is anticipated to bring 2.6 million more container units, produce about $70 million in revenue in the next five years and create more jobs, port officials said.

MSC is teaming up with Total Terminal International in Pier T, giving it access to 5,000 feet of berthing space and more than 96,000 feet of rail track.

And, with the signing of a 40-year lease, OOCL will take on most of the real estate in Middle Harbor, a massive terminal now under construction that is expected to handle more than 2 million additional containers when completed in 2019.